1. Field of the Invention
The present invention relates to a display module and a driving apparatus thereof, and more particularly, to a liquid crystal display module and a driving apparatus thereof.
2. Description of the Related Art
In general, liquid crystal display (LCD) devices are commonly used in display devices because of their light weight, thin profile, and low power consumption. For example, the LCD device are commonly used in office automation devices and audio/video devices. The LCD device displays images by adjusting light transmissivity according to image signals supplied to a plurality of control switches arranged in a matrix configuration.
Generally, LCD devices include an LCD module and a driving circuitry for driving the LCD module. The LCD module consists of an LCD panel having a plurality of liquid crystal cells arranged in a matrix configuration between two glass substrates, and a backlight unit for irradiating light onto the LCD panel. The LCD panel and the backlight unit are engaged with each other as an integral device so as to prevent light loss, and to prevent damage caused by external impact. Accordingly, there is provided a case for the LCD panel enclosing the back light unit including edges of the LCD panel.
There are two types of the back light units used with LCD panels: a direct-below-type; and an edge-type. The edge-type back light unit includes a fluorescent lamp installed at an exterior of a flat plate, wherein light produced by the fluorescent lamp is incident along an entire surface of the LCD panel through a transparent light guide plate. The direct-below-type back light unit has a light source arranged at a rear surface of the LCD panel, and directly radiates light along an entire surface of the LCD panel. As compared with the edge-type back light unit, the direct-below-type back light unit has an advantage that a plurality of light sources can be used, thereby improving brightness and increasing a light-emitting surface of the direct-below-type back light unit.
FIG. 1 is a perspective assembly view of an LCD module according to the related art, and FIG. 2 is a cross sectional view along I-I′ of FIG. 1 according to the related art. In FIGS. 1 and 2, an LCD module 1 includes a main support 14, a backlight unit 18, an LCD panel 6 stacked along an interior of the main support 14, and a case top 2 for enclosing edges of the LCD panel 6 and a side surface of the main support 14. Although not shown, an upper polarizing sheet is attached onto the upper substrate 5 of the LCD panel 6, and a lower polarizing sheet is attached onto a rear side of the lower substrate 3 of the LCD panel 6.
The LCD panel 6 includes an upper substrate 5 and a lower substrate 3, and a liquid crystal material injected between-the upper substrate 5 and the lower substrate 3. Although not shown, the LCD panel 6 is provided with a spacer for maintaining a uniform gap between the upper substrate 5 and the lower substrate 3.
The upper substrate 5 of the LCD panel 6 is provided with a color filter, a common electrode, and a black matrix (not shown), and the lower substrate 3 includes a plurality of signal lines (not shown), such as data lines and gate lines, and a thin film transistor (TFT) is formed at each intersection of the data lines and the gate lines. The TFT switches data signals to be transmitted along the data line to the liquid crystal cell in response to a scanning pulse (i.e., a gate pulse) transmitted along the gate line. In addition, a pixel electrode is formed at each pixel area defined by the intersection of the data line and the gate line.
One side of the lower substrate 3 is provided with a pad area connected-to each of the data line and the gate line. Although not shown, a tape carrier package (TCP), which includes a driver integrated circuit (IC) mounted thereon for supplying driving signals to the TFTs, is attached onto the pad area. The TCP supplies data signals from the driver IC to the data lines. In addition, the TCP supplies scanning signals to the gate lines.
In FIG. 1, the main support 14 is formed of a molded material, and its inner side wall surface is molded to have a step coverage face and a securing part, wherein the back light unit 18 and the LCD panel 6 are disposed on the step coverage face. The back light unit 18 is a direct below-type unit that irradiates light onto the LCD panel 6, wherein the LCD panel 6 and the back light unit 18 are stacked inside of the main support 14.
FIG. 3 is a perspective view of a back light unit of the LCD module of FIG. 1 according to the related art. In FIG. 3, the back light unit is a direct below-type back light unit and includes a plurality of lamps 20 irradiating light onto the LCD panel 6, a plurality of lamp holders 22 upon which the plurality of the lamps 20 are mounted, a diffuser 10 (in FIG. 1) diffusing incident light received from the plurality of the lamps 20 and irradiate the light onto the LCD panel 6, a lamp housing 18 arranged at a rear surface of the plurality of the lamps 20, and a plurality of optical sheets 8 stacked on the diffuser 10. The lamp housing 18 includes a reflection sheet 12 and a bottom cover 16 arranged on the rear surface of the reflection sheet 12.
Each of the plurality of lamps 20 is a cold cathode fluorescent lamp, wherein the lamps 20 include a glass tube, inert gases contained within the glass tube, and a cathode and an anode installed at opposite ends of the glass tube. The inert gases are injected into the glass tube, and phosphorus is applied to interior surfaces of the glass tube. The lamps 20 are grouped into an n-number of lamps (where n is a positive integer) which are mounted onto the lamp holder 22. Accordingly, the light generated from the lamps 20 is incident to the diffuser 10.
The diffuser 10 forces the light received from the lamps 20 to be directed toward a front surface of the LCD panel 6, thereby diffusing the light to produce a uniform distribution onto the LCD panel 6. The diffuser 10 includes a transparent resin film having opposing surfaces coated with light-diffusion materials.
In FIG. 3, the reflection sheet 12 is arranged along rear surfaces of the lamps 12, and has the same shape as the bottom cover 16. In addition, the reflection sheet 12 has a bottom surface overlapping the bottom surface of the bottom cover 16 and an inclination surface correspondingly bent to the inclination surface of the bottom cover 16. In addition, the bottom cover 16 has a bottom surface and an inclination surface extended from the bottom surface. For example, the bottom surface and the inclination surface of the bottom cover 16 are bent to have a stepped portion. Although not shown, the reflection sheet 12 is adhered to the bottom surface and the inclination surface of the bottom cover 16 by an adhesive tape. Accordingly, the reflection sheet 12 reflects light outgoing toward the rear surface and the side surface of the lamps 20 to the LCD panel 6, thereby improving light irradiation efficiency onto the LCD panel 6. In FIG. 3, the light radiated via the diffuser 10 is provided to the LCD panel 6 via the optical sheets 8 (in FIG. 1). The light radiated from the diffuser 10 provides diffused light, thereby increasing a viewing angle of the LCD panel 6. The efficiency of the light incident to the LCD panel 6 increases when the incident light is perpendicular to the LCD panel 6. Accordingly, the optical sheets 8 are disposed on the diffuser 10. The optical sheets 8 diffuse the light outgoing from the diffuser 10 and convert the light to be perpendicular to the LCD panel 6, thereby improving light efficiency.
In FIG. 2, the top case 2 has a square shape including a plane part and a side part bent perpendicularly to the plane part. Accordingly, the top case 2 serves to enclose the edges of the LCD panel 6 and the main support 14.
FIG. 4 is a schematic plan view of a color filter layer of the LCD module of FIG. 1 according to the related art. In FIG. 4, a color filter 25a has red R, green G, and blue B color pixels that are arranged in a stripe pattern, thereby transmitting light having specific wavelength bands to display colored light. Although not shown, a black matrix is formed between the red R, green G, and blue B color pixels of the color filter 25a. The black matrix separates the red R, green G, and blue B color pixels from each other and absorbs light received from an adjacent pixel, thereby preventing deterioration of image contrast.
Although not shown in FIG. 1, the LCD module 1 includes the color filter layer 25a and the back light unit of FIG. 3, wherein each of the colors of red R, green G, and blue B has a color wavelength band of more than 100 nm. In addition, wavelengths of other colors in addition to the colors of red R, green G, and blue B are produced, thereby deteriorating color purity, as shown in FIG. 5. However, in the LCD module 1, color purity of light passing through the color filter layer 25a is deteriorated to yield a low color representation ratio of 60% in comparison with a National Television System Committee (NTSC) standard, as shown in FIG. 6. Accordingly, increasing a thickness of the color filter 25a has been proposed to prevent the low color representation ratio. As a result, the color purity can be increased up to 80%. However, if the thickness of the color filter layer 25a is increased in order to increase the color purity, then the brightness of the LCD panel 6 is lowered by an amount of about 10%˜about 20%, which results in a deteriorated display quality of the LCD module 1.
FIGS. 7A and 7B are schematic plan views of color filter layers of the LCD panel of FIG. 1 according to the related art. In FIGS. 7A and 7B, in order to prevent deterioration of brightness and increase the color representation ratio by raising the color purity, a four-color filter layer 25b includes a yellow color filter Y. Accordingly, the color representation ratio is increased up to 60%˜70% in comparison with NTSC standard, as shown in FIG. 8A. Furthermore, if a five-color filter layer 25c includes a cyan color filter C, as shown in FIG. 7A, then the color representation ratio increases up to 70%˜80% in comparison with NTSC standard, as shown in FIG. 8B. Moreover, if a six-color filter layer includes a magenta color filter M (not shown) color, then the color representation ratio increases up to more than 80% in comparison with NTSC standard.
However, if the color filter layers 25b and 25c are applied to the LCD panel 6 of FIG. 1, aperture ratio decreases, as shown in Table 1. If the aperture ratio decreases, then light efficiency of the LCD module 1 is reduced. Thus, display quality deteriorates.
TABLE 1coloraperturechange ofcomparison ofcolorpixelsratioaperture ratioaperture ratioRGB340.83%0100% RGBY440.68% −0.4%99%RGBYC533.61%−17.6%82%RGBYCM619.64%−51.9%48%
In addition, since the number of data ICs increases as the number of color pixels increases, production costs for the LCD module 1 increases. Moreover, since processes for forming the color filter layers 25b and 25c are complicated, low yield of the LCD module 1 results.